Process of and apparatus for producing caustic solutions of high concentration



Sept. 16, 1952 c. DEPREZ ErAL PROCESS OF AND APPARATUS FOR PRODUCING CAUSTIC SOLUTIONS OF" HIGH CONCENTRATION Filed March 5, 1947 2 i 0r; T New ak Na m m A ATTORNEY Patented Sept. 16, 1952 UNITED STATES PATENT OFFICE 7 2,610,908 mosses 30F. AND APPAfi'A'fUS FOR PRO- DUGING GAUSTIC SOLUTIONS or HIGH CONCENTRATION Charles" Bosuettsw, Bortsfort-Brussels, Belgium, as?

is to solvaijfi Cie, Ixelles=B russels,"Bel-" gium; a; Belgian company This invention relates to process and a'oi iatfis for the decomposition of alkali swith production of caustic liquors highly concentrated in alkali hydroxides. It isflino'wii' that the satisfactory operation or these devices depends, among other factors, on the temperature condi tions; the heat evolved by' the rea'ction' isl, for the greater part, absorbed by the mercury and in the usual type of apparatus it is not well utilised.

A judicious l'ltilizatib fi of this heat is obtained with the process and apparatus as" described in Belgian Patent No. 454,461, dated February 18; 1944, in which heat is removed froin the their eury by vaporising part of the water'present' and condensing the resulting steam in the more highly concentrated liquor} thereby raising" the temperature of the latter and promoting theid'e composition of the ammgam; The opeiation' ,is carried out in a cell divided into compartments: a portion of the least conoentrated's'olution ifs'fi'r'st vaporised, then the vapour produced isjcondensed in a. compartment containing more'higlily concentrated solution, the temperature offwhich is raised until it veporises; the vapo'ur tlihs. prof du'ced at higher" temperatureiscondensedin turn ina compartment where the hydroxideiconcentration is still higher; and so on uptojthe compartment for the finished product Where the temperature is highest.

Thepresent invention hasioritsotijeetlto fur ther impr'ove said process andto;render the sa rne applicable to so-called ho'riz'ontal'cellsj the term horizontal being understood to mean slightly inclined in opposition to vertical or upward cells.

According to our inventionthe liciiior is led through the compartments of a horizontal cell and is caused to follow the? upper-wall ofZeach compartment over the greater part ofits le ngth, the passageway from one-compartmentto-the next being restricted-so that in: addition tothe liquor, only amounts of vapour and hydrogen substantially equal tothe amounts produced are allowed to pass; and said vapourand: gas are caused to enter the-next" compartment at the bottom thereof and'to bubble through the-liquor, whereby the vtfholeoftheheatevolve'd or; recovered in one cellpasses into the} nex compartment. To thisend; the venom-part ments are separated from one-anothei' by-two cross partitions, one forming an overflow and the other a liquid seal for the'solutio'n. v I

In order that the invention'i in nior'e clearly understood we shalldescribefbyiway of e amp e two embodiments thereof with. reference toithe ccompany ng drawings in which:

Fig". 1' diagrammatically illustratsin sectional side elevation a horizontal cell according to our inven i n; Y, i

Fi' 2 ikewise; inustroites a modified ceir ac corcihgto'our ventio g In the eiiamplefillus'tratedin Fig. 1,' the hori zohtaioen provided witht iensoer heat 'ns'ulated alls is divided int'o" apmrant mr ompartments A, B, 31;, o, each,orwhich niay'fbe built as a. s parate section' an'd then connected with the others; Each com ar ment is separated jfroin the next one by two cross" ,pazftit'iofns; one par: titioni l' ooerat hgtes an ove nowor r th' solution f token ydroxide andjpitojecting downwar l into a depie'sio'rii 3111 the ama1g amiqrms a liquid seal, the'other partition 'z forming a gas trap and projecting downwardly intojthe. Solution to a small distance above the level of the ama m; f Water'is introducedintotcompartment Axwhich is provided with heatfexchange ribs" 410i extensive surface, which are secured tojlth'e bottom of the apparatus and are licked by theaquequs solution. The" other" compartments have .a' fiat bottom on whicli arefappliedgrids Sin a known manner, in order) to promote: decomposition; of the amalgam. The last eompartmentC is'pro vided with a gas delivery dome 6 and, an'pu'ts b 1 r ee tndit nisheds lution 'rhe cen s closed etib th ndsibv arts formin 1iquid"s ea1 s,, onef D for letting out the mercury, the' other E tor. letting n the amalgam; r grids 5' are made of graphite and are strongly pressedja'ga'inst the fiat amalgamated: bottom of the'c'el i a t The amalgamissuppliedjo the head E. of the apparatus'thifough a" tube v8f dipping in the liquid illfl": iii Q 'fi W n' f l m w 'h i is s t prea we th I m j inat 611 be emi te ew' 'i ei mt r m m'ie t e e tisno theg'ri'dsj' and passing" under the titionsf through the depressions 3 11" V u practically decomposed, it reaches the r s te- P e t w i rxa r v ou t ted; he? 1 b ri b t; hea chan r s orfl let is' iit i tothebot Om-j 1 Thence the; mercury" its] from amen roriris t eiliquio eerie a d is y nw e o w 'mfl to j The water neces ary for; forming? the caustic solution follows ai -"opposite mitted to" compartment p r urraed ,ah r s. frets t tia'l" partof the heat containedtherei s eer tion of the water is vaporised. The water-vapour mixture flows towards the partition I and over the same into the space comprised between partitions l and 2, and enters the compartment B through the restricted space under partition 2. The vapour condenses in the liquid in B until this liquid in turn evolves vapour, this occurring at a temperature higher thanin compartment A since the concentration m3 is higher. This operation is repeated as the solution proceeds from one compartment to the next and the maximum temperature is reached.

The process is preferably carried out under such conditions that the gas chambers above the solution are practically reduced to nil. To this end the partitions I are carried to such height that the solution is in contact with the top wall of the cell over the greater part thereof, and the passageway between the top wall and the partition I is reduced to the opening just necessary to allow passage of the caustic solution and of the water'vapour and hydrogen produced. In this way the whole of the heat evolved or recovered in a compartment such as B1 passes into the next compartment B2 owing to the fact that the vapour and hydrogen have to bubble through the solution in B2; the hydrogen having previously yielded part of its heat to the solution in B1 since it had in the form of bubbles a prolonged contact with the latter solution on account of the absence of a gas chamber. Without the arrangement as described the hydrogen and water vapour would leave the cell carrying their own heat at the expense of the output of the cell. This arrangement moreover results in energetically stirring the liquor in each compartment, thus creating conditions favourable to a better heat exchange with and a quicker decomposition of the amalgam.

The hydrogen evolved in the successive compartments accumulates in the dome of section C and flows with the solution through pipe I into a separator ll of known type.

The apparatus also comprises vapour inlets (not shown) in the chambers between partitions I and 2 and in the liquid seals 3, 9, l2, their purpose being chiefly to blow steam to clean and remove occasional obstructions produced by the amalgam.

The cell as described may be used for decomposing amalgam supplied by a plurality of electrolytic cells; valves for stopping the supply of mercury then being provided in a known manner in order to avoid short-circuiting the cells.

The operation of the apparatus described is methodical since the amalgam and the solution flow in Opposite directions. This is of advantage when the amalgam produced in the electrolytic cell enters the apparatus at a high temperature. In the general case where the average range of temperatures is lower in the electrolytic cell than in the decomposition cell, it may be advantageous to introduce the amalgam no longer into the solution outlet compartment, but into another compartment of lower temperature. Two decomposition cells as described then may be connected in series; one in which the amalgam and the solution flow in the same direction, the second in which they flow in opposite directions.

A preferred arrangement, as regards the operation, consists in combining both cells into a single apparatus as shown by way of example in Fig. 2. Taking the apparatus of Fig. l, a portion thereof comprising the compartments Bn-l, B1,, is inverted and the solution is led directly from B2 to E near the amalgam inlet through an inner or outer pipe [3. This pipe [3 also conveys the water vapour and the hydrogen evolved in the compartments A, B1, B2 and feeds them into the compartment E through a perforated down-turned distributor. In order to provide a contact between the solution and the top wall of the cell over a surface as large as possible, the top wall as shown is inclined at an angle opposite to the angle of the bottom with respect to the horizontal. Thus, as shown in Fig. 2, wherein the inlets and outlets for the materials handled are designated by the same reference numbers used in Fig. 1 and employed in the foregoing description of the process of the invention,

' and wherein the flow of materials is shown by arrows and appropriate legends, the amalgam and the alkali metal hydroxide solution formed by the reaction of water with the amalgam, are in contact in an area of counter-current flow and are in contact in an areaof co-current flow. Thus, referring to Fig. 2, the amalgam to be treated is introduced through tube 8, dipping into a liquid seal 9. Water is supplied through the water inlet designated H2O. In the lefthand portion of the apparatus in Fig. '2, the amalgam flows to the left and the alkali metal hydroxide above the amalgam flows to the right. Thus, these two materials flow counter-currently. In the right-hand portion of the apparatus. of Fig. 2,. the amalgam flows to the left and the alkali metal hydroxide also flows to the left, i. e. in co-current flow. From the end of the area of counter-current flow which is opposite the end intqwhich the wateris introduced the alkali metal hydroxide is'carried through the pipe [3 inthe direction of the arrows tothe end of the area of co-current flow atwhich the fresh amalgam is introduced. At the'opposite end of the area of co-current flow,,the alkali metal hydroxide solution is removed through outlet pipe 1 and the amalgam, which is partially denuded at this. point by reason of the previous contact with the alkali metal hydroxide solution, passes into the portion of the apparatus in which there is counter-current flow and finally passes out of the apparatus through outlet l2 as indicated by the arrow in Fig. 2 at the end at which water is introduced. It will be seenby reference to Fig. 2 thatthe alkali metal hydroxide solution flows unidirectionally toward the right in the area of counter-current flow (left-hand portion of Fig. 2) and that the alkali metal hydroxide solution flows unidirectionally toward the left in the area of co-current flow (right-hand portion of Fig. 2); Further, it will be seen that the vapors and the liquid are both caused to flow unidirectionally andthat the vapors from one body of alkali metal hydroxide solution are caused to pass through the adjacent body of alkali metal hydroxide solution, as previously pointed out in connection with the description of Fig. 1. By reason of the continuous contact with richer amalgam in passing through the apparatus the alkali metal hydroxide solution increases in concentration in the direction of flow of the solution. Thus, in Fig. 2, the alkali metal hydroxide solution increases in concentration from left to right in the left-hand portion of Fig. 2 and from right to left in the right-hand portion of Fig. 2.

It will be understood that the invention is not limited to the constructional details herein shown and described, but it may be modified within the scope of the appended claims as by making the compartmentsin the form of separate receptacles. 4

We claim: r r

1. In an apparatus for the decomposition of alkali metal amalgam by water, in combination, an elongated substantially horizontal trough, means defining a confined area adapted for coun ten-current material flow in said trough, means defining aconfined area of' co-current material flow; in said trough, said trou h having a sloping bottom; a top; and side walls, a water inlet and a m-ercuryoutlet at one end of said area ofcounter-ourrentflow, an amalgam inlet at one end of said area of co-currentflow and a solution outlet at the other end of saidarea of co-current flow, the top of said trough adjacent said mercury outlet being substantially parallel to said slopedbottom. and the bottom and top: of said trough adjacent said amalgam inlet converging toward said amalgaminletipartition means between said area of counter-current flow and said area of co-current flowandj conduit means extending from the upper'portion of said area of counter-current'flow to the portion of said area of co-current flow adjacent said amalgam inlet for conducting fluids from said area of countercurrent flow to said area of co-current flow.

2. In an apparatus for the decomposition of alkali metal amalgam by water, in combination, an elongated substantially horizontal trough, means defining, a confined area adapted for countor-current material flow in said trough, means defining a confined area of co-current material flow in said trough, said trough having a sloping bottom, a top, and side walls, a Water inlet and a mercury outlet at one end of said area of counter-current flow, an amalgam inlet at one end of said area of co-current flow, and a solution outlet at the other end of said area of co-current flow, the top of said trough adjacent said mercury outlet being substantially parallel to said sloped bottom, and the bottom and top of said trough adjacent said amalgam inlet converging toward said amalgam inlet, partition means between said area of counter-current flow and said area of co-current flow, said amalgam inlet means and said solution outlet means being at opposite ends of said area of co-current flow, said solution outlet means being adjacent said partition means separating said area of counter-current flow from said area of co-current flow, and conduit means extending from the upper portion of said area of counter-current flow to the portion of said area of co-current fiow adjacent said amalgam inlet for conducting fluids from said area of counter-current flow to said area of co-current flow.

3. A process of producing alkali metal hydroxide solutions of high concentration by decomposing the corresponding alkali metal amalgams which comprises, establishing a plurality of sub stantially-horizontal confined reaction zones containing alkali metal hydroxide solution, the solution in each of said zones increasing in alkali metal hydroxide concentration at a first end of least concentration to a zone of highest concentration, said zones defining a confined area of counter-current flow including said zone of least concentration and a confined area of co-current flow including said zone of highest concentration, introducing water into said zone of least alkali metal hydroxide concentration at a first end of said area of counter-current flow, introducing alkali metal amalgam into a first end of said area of co-current flow, flowing said amalgam unid' ectionall'yfrom said-first and afssaidlarea of; c r'rent flowto the second zend'ot said area of eta-current flow i 'ntroducing alkali metalamal gain. from said secondend or. saidi a-rea of co-. current flow into the second endto'i said: area of. counter-currentflow, flowing said. amalgam unidirectionally'from said second end' to said first end of said area of counter-current fi'o'w, and flowing alkali metal hydroxidesolution and va-' pors, including water vapor generated therein, unidirectionally from said first end to said second end of said area of counter-current-flbw, where-- bysaid amalgam-flows counter-currently tosaid solution and said vaporsthroughout said area'of counter current Vfiow, transr"erri'ng alkalimet'al hydroxide solution and vapor-s, i-ncluding watervapor generatedtherein, through a eonfined transport zone from said second? end of 'said area ofcounter-current flow' 'to Samara end of said area of cocurrent' flow, the sol-utiorrand vapors in said area of counter-current fiow being other wise isolated 'from said area ofco-currentflow, flowing alkali metal hyd'roxi'de solution and va-- pors, including water vapor generated therein,

' unidirectionally'from said first end to said second end of said area of -co-current flow, whereby the amalgam'introducedi'into said first end of said area..,co:-'current.fiow flows co-currently to said solution and said vapors throughout said area of co-current flow, Withdrawing alkali metal hydroxide solution from said zone of highest concentration at said second end of said zone of cocurrent flow, said alkali metal hydroxide solution and said vapors, including water vapor, being introduced from each of said zones into the next zone of higher concentration into the lower portion thereof, whereby the vapors passing to said zone of-higher concentration are caused to pass through the solution in said zone and the water vapors to condense therein.

4. A process of producing alkali metal hydroxide solutions of high concentration by decomposing the corresponding alkali metal amalgams which comprises, establishing a plurality of substantially-horizontal confined reaction zones containing alkali metal hydroxde solution, the solution in each of said zones increasing in alkali metal hydroxide concentration from a zone of least concentration to a zone of highest concentration, said zones defining a confined area of counter-current flow including said zone of least concentration and a confined area of co-current flow including said zone of highest concentration, introducing water into said zone of least alkali metal hydroxide concentration at a first end of said area of counter-current flow, introducing alkali metal amalgam into a first end of said area of co-current flow, flowing said amalgam unidirectionally from said first end of said area of co-current flow to the second end of said area of co-current flow, introducing alkali metal amalgam from said second end of said area of cocurrent flow into the second end of said area of counter-current flow, flowing said amalgam unidirectionally from said second end to said first end of said area of counter-current flow, and flowing alkali metal hydroxide solution and vapors, including water vapor generated therein, unidirectionally from said first end to said second end of said area of counter-current flow, whereby said amalgam flows counter-currently to said solution and said vapors throughout said area of counter-current flow, transferring alkali metal hydroxide solution and vapors, including water vapor generated therein, through a confined transport zone from said second end of said area of counter-current flow to said first end of said area of co-current flow, the solution and vapors in said area of counter-current flow being otherwise isolated iromsaid area of co-current flow, flowing alkali metal hydroxide solution and vapors, including water vapor generated therein, unidirectionally from said first end to said second end of said area of co-current flow, whereby the amalgam introduced into said first end of said area of co-current flow flows co-currently to said solution and said vapors throughout said area of co-current flow, withdrawing alkali metal hydroxide solution from said zone of highest concentration at said second end of said zone of cocurrent flow, said alkali metal hydroxde solution and said vapors, including water vapor from each of said zones being caused to follow the upper portion of the zone over the greater part of its length, being removed from adjacent the top of one zone and being introduced from each of said zones into the next zone of higher concentration into the lower portion thereof, whereby the vapors passing to said zone of higher concentration are caused to pass through the solution in said zone and the water vapor to condense therein.

" CHARLES DEPREZ.

ALEXIS BASILEWSKY.

8, REFERENCES CITED The following references are of record in the file of this patent:

? UNITED STATES PATENTS v I Date Number Name 679,355 Barr July 30, 1901 728,746 7 McCafirey May 19, 1903 908,545 Carrier Jan. 5, 1909 930,909 j Wie gand Aug. 10, 1909 1,121,532 I Newberry Dec. 15. 1914 1,753,015 McGregor Apr. 1; 1930 2,083,648 Gorke June 5, 1937 2,392,236 Edwards Jan. 1, 1946 p FOREIGN PATENTS Number Country Date.

4,448 Great Britain 1874 17,169 Greatv Britain 1892 10,352 Great Britain 1909 453,517. "Great Britain 1936 615,523 1 Germany 1935 643,157 Germany Mar. 10, 1937 136,768

Switzerland 1930 

3. A PROCESS OF PRODUCING ALKALI METAL HYDROXIDE SOLUTIONS OF HIGH CONCENTRATION BY DECOMPOSING THE CORRESPONDING ALKALI METAL AMALGAMS WHICH COMPRISES, ESTABLISHING A PLURALITY OF SUBSTANTIALLY-HORIZONTAL CONFINED REACTION ZONES CONTAINING ALKALI METAL HYDROXIDE SOLUTION, THE SOLUTION IN EACH OF SAID ZONES INCREASING IN ALKALI METAL HYDROXIDE CONCENTRATION AT A FIRST END OF LEAST CONCENTRATION TO A ZONE OF HIGHEST CONCENTRATION, SAID ZONES DEFINING A CONFINED AREA OF COUNTER-CURRENT FLOW INCLUDING SAID ZONE OF LEAST CONCENTRATION AND A CONFINED AREA OF CO-CURRENT FLOW INCLUDING SAID ZONE OF HIGHEST CONCENTRATION, INTRODUCING WATER INTO SAID ZONE OF LEAST ALKALI METAL HYDROXIDE CONCENTRATION AT A FIRST END OF SAID AREA OF COUNTER-CURRENT FLOW, INTRODUCING ALKALI METAL AMALGAM INTO A FIRST END OF SAID AREA OF CO-CURRENT FLOW, FLOWING SAID AMALGAM UNIDIRECTIONAILTY FROM SAID FIRST END OF SAID AREA OF CO-CURRENT FLOW TO THE SECOND END OF SAID AREA OF CO-CURRENT FLOW, INTRODUCING ALKALI METAL AMALGAM FROM SAID SECOND END OF SAID AREA OF COCURRENT FLOW INTO THE SECOND END OF SAID AREA OF COUNTER-CURRENT FLOW, FLOWING SAID AMALGAM UNIDIRECTIONALLY FROM SAID SECOND END TO SAID FIRST END OF SAID AREA OF COUNTER-CURRENT FLOW, AND FLOWING ALKALI METAL HYDROXIDE SOLUTION AND VAPORS, INCLUDING WATER VAPOR GENERATED THEREIN, UNIDIRECTIONALLY FROM SAID FIRST END TO SAID SECOND END OF SAID AREA OF COUNTER-CURRENT FLOW, WHEREBY SAID AMALGAM FLOWS COUNTER-CURRENTLY TO SAID SOLUTION AND SAID VAPORS THROUGHOUT SAID AREA OF COUNTER-CURRENT FLOW, TRANSFERRING ALKALI METAL HYDROXIDE SOLUTION AND VAPORS, INCLUDING WATER VAPOR GENERATED THEREIN, THROUGH A CONFINED TRANSPORT ZONE FROM SAID SECOND END OF SAID AREA OF COUNTER-CURRENT-FLOW TO SAID FIRST END OF SAID AREA OF CO-CURRENT FLOW, THE SOLUTION AND VAPORS IN SAID AREA OF COUNTER-CURRENT FLOW BEING OTHERWISE ISOLATED FROM SAID AREA OF CO-CURRENT FLOW, FLOWING ALKALI METAL HYDROXIDE SOLUTION AND VAPORS, INCLUDING WATER VAPOR GENERATED THEREIN, UNIDIRECTIONALLY FROM SAID FIRST END TO SAID SECOND END OF SAID AREA OF CO-CURRENT FLOW, WHEREBY THE AMALGAM INTRODUCED INTO SAID FIRST END OF SAID AREA CO-CURRENT FLOW FLOWS CO-CURRENTLY TO SAID SOLUTION AND SAID VAPORS THROUGHOUT SAID AREA OF CO-CURRENT FLOW, WITHDRAWING ALKALI METAL HYDROXIDE SOLUTION FROM SAID ZONE OF HIGHEST CONCENTRATION AT SAID SECOND END OF SAID ZONE OF COCURRENT FLOW, SAID ALKALI METAL HYDROXIDE SOLUTION AND SAID VAPORS, INCLUDING WATER VAPOR, BEING INTRODUCED FROM EACH OF SAID ZONES INTO THE NEXT ZONE OF HIGHER CONCENTRATION INTO THE LOWER PORTION THEREOF, WHEREBY THE VAPORS PASSING TO SAID ZONE OF HIGHER CONCENTRATION ARE ACUSED TO PASS THROUGH THE SOLUTION IN SAID ZONE AND THE WATER VAPORS TO CONDENSE THEREIN. 